Optimize getndelim2 to use block operations when possible.

* modules/getndelim2 (Depends-on): Add stdbool, freadptr,
freadseek, and memchr2.
* lib/getndelim2.c (getndelim2): Use them for block reads.

Signed-off-by: Eric Blake <ebb9@byu.net>

diff --git a/ChangeLog b/ChangeLog
index ab0e29275a8de3db9f9a3a13e866aeeb02962297..5cf1dd3f2ba4122b918f37b04e00496f15c3ad02 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2008-04-29  Eric Blake  <ebb9@byu.net>
+
+       Optimize getndelim2 to use block operations when possible.
+       * modules/getndelim2 (Depends-on): Add stdbool, freadptr,
+       freadseek, and memchr2.
+       * lib/getndelim2.c (getndelim2): Use them for block reads.
+
 2008-04-29  Bruno Haible  <bruno@clisp.org>
 
        * m4/inet_ntop.m4 (gl_INET_NTOP): Require gl_USE_SYSTEM_EXTENSIONS.

diff --git a/lib/getndelim2.c b/lib/getndelim2.c
index 8930a5bd369f12b2f06d9623f635e288e44d7391..be34e40e6104b35324e98549645ca36bb98d48d7 100644 (file)
--- a/lib/getndelim2.c
+++ b/lib/getndelim2.c
@@ -23,8 +23,10 @@
 
 #include "getndelim2.h"
 
-#include <stdlib.h>
+#include <stdbool.h>
 #include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
 
 #if USE_UNLOCKED_IO
 # include "unlocked-io.h"
@@ -41,6 +43,10 @@
 #include <limits.h>
 #include <stdint.h>
 
+#include "freadptr.h"
+#include "freadseek.h"
+#include "memchr2.h"
+
 #ifndef SSIZE_MAX
 # define SSIZE_MAX ((ssize_t) (SIZE_MAX / 2))
 #endif
@@ -63,6 +69,7 @@ getndelim2 (char **lineptr, size_t *linesize, size_t offset, size_t nmax,
   ssize_t bytes_stored = -1;
   char *ptr = *lineptr;
   size_t size = *linesize;
+  bool done = false;
 
   if (!ptr)
     {
@@ -81,23 +88,62 @@ getndelim2 (char **lineptr, size_t *linesize, size_t offset, size_t nmax,
   if (nbytes_avail == 0 && nmax <= size)
     goto done;
 
+  /* Normalize delimiters, since memchr2 doesn't handle EOF.  */
+  if (delim1 == EOF)
+    delim1 = delim2;
+  else if (delim2 == EOF)
+    delim2 = delim1;
+
   flockfile (stream);
 
-  for (;;)
+  while (!done)
     {
       /* Here always ptr + size == read_pos + nbytes_avail.  */
 
       int c;
+      const char *buffer;
+      size_t buffer_len;
+
+      buffer = freadptr (stream, &buffer_len);
+      if (buffer)
+       {
+         if (delim1 != EOF)
+           {
+             const char *end = memchr2 (buffer, delim1, delim2, buffer_len);
+             if (end)
+               {
+                 buffer_len = end - buffer + 1;
+                 done = true;
+               }
+           }
+       }
+      else
+       {
+         c = getc (stream);
+         if (c == EOF)
+           {
+             /* Return partial line, if any.  */
+             if (read_pos == ptr)
+               goto unlock_done;
+             else
+               break;
+           }
+         if (c == delim1 || c == delim2)
+           done = true;
+         buffer_len = 1;
+       }
 
       /* We always want at least one byte left in the buffer, since we
         always (unless we get an error while reading the first byte)
         NUL-terminate the line buffer.  */
 
-      if (nbytes_avail < 2 && size < nmax)
+      if (nbytes_avail < 1 + buffer_len && size < nmax)
        {
          size_t newsize = size < MIN_CHUNK ? size + MIN_CHUNK : 2 * size;
          char *newptr;
 
+         if (newsize < buffer_len)
+           newsize = buffer_len + size;
          if (! (size < newsize && newsize <= nmax))
            newsize = nmax;
 
@@ -118,25 +164,20 @@ getndelim2 (char **lineptr, size_t *linesize, size_t offset, size_t nmax,
          read_pos = size - nbytes_avail + ptr;
        }
 
-      c = getc (stream);
-      if (c == EOF)
+      if (1 < nbytes_avail)
        {
-         /* Return partial line, if any.  */
-         if (read_pos == ptr)
-           goto unlock_done;
+         size_t copy_len = nbytes_avail - 1;
+         if (buffer_len < copy_len)
+           copy_len = buffer_len;
+         if (buffer)
+           memcpy (read_pos, buffer, copy_len);
          else
-           break;
+           *read_pos = c;
+         read_pos += copy_len;
+         nbytes_avail -= copy_len;
        }
-
-      if (nbytes_avail >= 2)
-       {
-         *read_pos++ = c;
-         nbytes_avail--;
-       }
-
-      if (c == delim1 || c == delim2)
-       /* Return the line.  */
-       break;
+      if (buffer && freadseek (stream, buffer_len))
+       goto unlock_done;
     }
 
   /* Done - NUL terminate and return the number of bytes read.

diff --git a/modules/getndelim2 b/modules/getndelim2
index 972ee1a4cde5d35742740d1e7a7aa77ed1b6faf8..51a63bfc5866cf4c85ce93dc96022926da89d305 100644 (file)
--- a/modules/getndelim2
+++ b/modules/getndelim2
@@ -9,7 +9,11 @@ m4/getndelim2.m4
 
 Depends-on:
 ssize_t
+stdbool
 stdint
+freadptr
+freadseek
+memchr2
 
 configure.ac:
 gl_GETNDELIM2